Ammagnostus antarcticus Bentley, Jago & Cooper 2009

• Main Authors: Smith, Patrick M., Paterson, John R., Brock, Glenn A.
• Format: Other/Unknown Material
• Language: unknown
• Published: Zenodo 2018
• Subjects: Biodiversity; Taxonomy; Animalia; Arthropoda; Trilobita; Agnostida; Agnostidae; Ammagnostus; Ammagnostus antarcticus; Antarc*; antarcticus
• Online Access: https://doi.org/10.5281/zenodo.5980800; http://treatment.plazi.org/id/038CC426FFA4FF84FF399DE9FEE4FDFB

Ammagnostus antarcticus Bentley, Jago & Cooper, 2009 Fig. 5 ?1967 Agnostoglossa bassa Öpik, p. 146, pl. 60, figs 6–14, text-fig. 44. ?1989 Ammagnostus sp. indet.; Wang, Mills, Webby & Shergold, p. 111, fig. 4A–D. 2009 Ammagnostus antarcticus Bentley, Jago & Cooper, p. 171, 172, fig. 4A–I. Material. Nineteen cephala and eight pygidia figured, CPC42177–CPC42203. 26 cephala and eleven pygidia not figured (mostly fragments). Description. Cephalon and pygidium each attaining about 2.6 mm in length; nonscrobiculate; surface smooth. Cephalon subquadrate in outline, about 94% as long as wide, nonspinose, moderately convex; border reasonably wide (sag., exsag.), flattened; border furrow well developed; preglabellar median furrow faintly developed or absent. Glabella 70–73% (mean 71%, n = 4) as long (sag.) as cephalon. Small anterior lobe clearly defined, semiovate in shape, obtusely angular to rounded anteriorly, occupying 29–30% (mean 30%, n = 4) of glabellar length. F3 deeply incised, strongly bowed rearward in a V-shape, bowing is weaker in smaller specimens. Posterior glabellar lobe wider (tr.) than anterior lobe, slightly tapers forward, convexity similar in both lobes. F2 furrows at glabellar mid-length (sag.), moderately developed as distinct notches, gently directed anteriorly for a short distance. F1 furrows effaced. Glabellar node indistinct, located slightly posterior of F2 furrows; basal lobes small, subtriangular in outline. Pygidium rounded to weakly quadrate in outline, 90% as long as wide, moderately convex, with short (exsag.) posterolateral spines, situated level with widest point in pygidial axis; border flattened, wide (sag., exsag.) and narrows distinctly toward anterior; border furrow moderately deep and wide (sag., exsag.). Axis wide (tr.) and long (sag., exsag.), reaching posterior border furrow; about 64 to 70% (mean 67%, n = 5) as wide as long and occupying 73% of pygidial length (sag.); slightly constricted across M2 and expanding to become wider behind F2; posteriorly rounded ...